22 EVOLUTION OF THE EARTH 



The temporary dispersal of the solar mass would lead to 

 an enormous increase in its radiant energy. The planetesimal 

 matter would as a consequence of its dispersion and increased 

 radiating surface cool with great rapidity, except in the nuclei 

 of masses, and cease to be self-luminous, the smaller particles 

 almost immediately becoming cold except as they were heated 

 by the larger and profoundly disturbed solar mass. 



The new stars which have been observed are not regarded 

 as of this nature since they are not expanded into a spiral. In 

 fact, as previously mentioned, no examples are known which 

 serve as illustrations, in the terms of this hypothesis, of the 

 birth stage of planetary systems. This lack of examples may 

 be connected with the small scale as well as the temporary 

 character of such a nebula. The whole solar system, extend- 

 ing to the orbit of Neptune, would subtend slightly less than 

 half a minute of arc as seen from the nearest star. The 

 average star is hundreds of times farther away and at the 

 greater distances a nebula of this order would not betray its 

 existence by its form but only by the temporary great increase 

 in radiance at the time of its birth. 



Chances of close approach. Whether the chance is great 

 or small of a planetary system being generated from any 

 particular star by tidal disruption. cannot be used as an argu- 

 ment for or against this hypothesis unless it were known what 

 proportion of the stars possessed planetary systems. But that 

 knowledge is hopelessly concealed from us in the depths of 

 space, since such a system as ours after its temporary initial 

 brilliance would, as shown, be invisible in the most powerful 

 telescopes even if it existed about the nearest star. 



It is not known how near an approach would be necessary 

 to generate such a solar system; but the chances of close 

 approach must be very small for any particular star. The 

 motion at any instant of any individual star is the result of its 

 motion inherited from the past plus the attractions of all the 



